Field of the Invention
The present invention relates to a probe configured to perform at least one of transmission or reception (hereinafter also referred to as “transmission/reception”) of an ultrasound wave such as an ultrasonic wave through use of a capacitive transducer, and to an object information acquiring device including the probe, such as an ultrasonic diagnostic apparatus. The term “ultrasound wave” is used as a term including a sound wave, an ultrasonic wave, an optical ultrasound wave, and other such waves, but in the following description, the ultrasound wave is sometimes represented by an ultrasonic wave.
Description of the Related Art
For the purpose of transmitting or receiving an ultrasonic wave, there has been proposed an ultrasonic probe using a capacitive micromachined ultrasonic transducer (CMUT), which is a capacitive ultrasonic transducer. A CMUT device requires a high and DC-potential bias voltage for maintaining a voltage across electrodes at a predetermined voltage. The CMUT device is a transducer whose electromechanical coupling coefficient changes depending on the magnitude of the bias voltage, and whose conversion characteristic increases as the bias voltage increases. When the bias voltage applied to the CMUT exceeds a certain predetermined value, displacement of a vibrating membrane of the CMUT changes drastically, and the vibrating membrane starts to be brought into contact with a substrate. This phenomenon is called “pull-in”, and the bias voltage at the time when the pull-in occurs is defined as “pull-in voltage”. When the phenomenon called “pull-in” occurs, the vibrating membrane and the substrate are brought into contact with each other, and the CMUT functions in a manner greatly different from what is originally expected as a transducer. The CMUT device is therefore required to be used at a bias voltage value lower than the pull-in voltage. The bias voltage value to be applied to the CMUT device is required to be determined individually for each device in consideration of a difference in pull-in voltage due to manufacturing variations and specifications that are based on an electromechanical coupling coefficient.
In an ultrasonic diagnostic apparatus disclosed in Japanese Patent No. 5303472, a memory storing a bias voltage value is mounted inside an ultrasonic probe. The ultrasonic diagnostic apparatus is configured to read the bias voltage value from the memory of the ultrasonic probe to set a value of a bias voltage to be supplied to the ultrasonic probe.
However, in the invention disclosed in Japanese Patent No. 5303472, it is required to provide, in the probe, a storage unit configured to store the bias voltage value and a communication unit and provide, in the ultrasonic diagnostic apparatus, a bias voltage control unit and a communication unit configured to communicate to/from the communication unit of the probe. Moreover, processing for controlling those units is also required.